This invention relates to high energy density plasma systems and, more particularly, to the adaptation of electron accelerators to produce high energy plasmas for use in commercial applications. This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The government has certain rights in the invention.
High energy density plasmas have broad industrial applications; for example as radiation sources with radiation in the extreme ultraviolet (XUV or soft x-ray range, i.e., wavelengths less than about 100 nm) that are used as photolithography sources in the manufacture of semiconductor integrated circuits (ICs). Other pertinent industrial and commercial applications include high temperature fusing of materials and fabrication of new materials like silica, carbon composites, and advanced ceramics. The capabilities of available imaging equipment limit component development and manufacturing. A next generation of lithography is proposed to provide ICs with features of less than 100 nm using lithography systems that produce 10 nm radiation. Current proposals are for x-ray synchrotrons to be the source of the needed 10 nm radiation.
X-ray synchrotron lithography systems, however, are large in cost and in size and are not likely to be widely available. Accordingly, there is some development in alternate devices, such as laser-produced plasma x-ray systems and z-pinch plasma sources. However, both of these systems involve high density plasmas that contact metal, causing particulate blow-off that impinges on and degrades nearby optical elements. Also, the rapid consumption of metal target foils (used in laser systems) or metal electrodes (used in z-pinch systems) inhibits or degrades continuous operation. Finally, although the output radiation power is acceptable (marginally), the power is released in very high peak-power units with rather low repetition rates (about 10 Hz for z-pinch and about 1000 Hz for laser based). As a result, quantized radiation is produced, causing IC chip manufacturers to be concerned about a lack of the pulse-to-pulse uniformity needed during a continuous chip exposure production process.
Accordingly, it is an object of the present invention to provide a high energy density plasma as a XUV radiation source as an alternate to x-ray synchrotron, laser-produced plasma, and z-pinch plasma sources.
Another object of the present invention is to provide pulsed plasma radiation sources with a high degree of pulse-to-pulse uniformity.
One other object of the present invention is to provide a plasma source capable of continuous operation through closed cycle recovery and reuse of a high pressure gas that is ionized to form the high energy density plasma.
Still another object of the present invention is to produce a high energy density plasma from a free-standing atmospheric jet rather than solid metal foils or electrodes to avoid material wear and concomitant solid particulate contaminants.
Yet another object of the present invention is to provide plasma pulses with higher irradiance than plasma pulses produced by lasers.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.